Nowhere Man essentially describes Mimic's entire history, he's had no real purpose, no real goal, even his powers depend on other people....
Helter Skelter is forever connected with Charles Manson and was his term for an apocalyptic race war. I'm not familiar with Omega so don't know if it fits.
Eleanor Rigby concerns a woman defined by loneliness who wears a different face to the outside world (She keeps it in a jar by the door). Mystique is isolated from everyone she has ever claimed to love (To be fair, mostly because she's a psychotic bitch) and when it comes to wearing a different face...